Tools used to fish objects from a bore hole are well known in the well drilling industry to remove the object from the bore hole and permit resumption of drilling or pumping operations. There are basically two types of these tools used, the spear and the overshot. The spear is lowered into the bore hole, engages the interior of the object and withdrawn from the hole with the object attached. The overshot is lowered into the bore hole, engages the exterior of the object and withdrawn from the hole with the object attached.
A relatively recent development in both types of these tool designs has been a tool that repetitiously moves between opened and closd positions. Thus, if the object is not grabbed on the first attempt, the tool is recycled for another attempt without withdrawing the tool from the bore hole. The overshot tools use a tubular body supporting fingers movable between the opened and closed positions. A spring is mounted within the body to urge the fingers toward the lower end of the body, which causes the fingers to move toward the closed position by coacting with a tapered surface located on the body. A camming mechanism is provided to control the movement of the fingers by using a sleeve rotatably mounted within the body which forms a cam face defining upwardly extending stems of "J" slotted grooves at the closed and opened positions of the fingers with connecting grooves between the "J" slotted grooves to create a single cam groove and permit recycling of the fingers between the opened and closed positions. Two pins extend from the body into and coact with the cam groove to cause the sleeve to rotate from the opened position to the closed position by moving the body toward and away from the object after engagement with a portion of the object. This action permits the pins to move up the stems of the "J" slotted groove and cause the spring to urge the fingers into the closed position or overcomes the urging of the spring to move the fingers into the opened position. Sometimes, the cam face of the sleeve defines a slot in the cam groove extending downwardly at each position between the upwardly extending stems of the "J" slotted grooves. This camming mechanism has created severe difficulties in these tools because the pins frequently strike the ends of the slots in the cam groove. Thus, the pins have a tendency to break within the cam groove and damage the cam face. The frequency of pin breakage increases as stronger springs are used, which is desired for providing a stronger gripping force by the fingers on the object. Further, this pin breakage can cause damage to the fingers because the fingers will extend downwardly past the end of the body after the pin breaks. In such condition, the fingers are jammed into the fish without the user knowing that the tool is not recycling.
Another problem existing in the construction of the prior art tools has to do with the difficulty in aligning two pins symmetrically within the body for coacting within the cam groove. Should the pins be misaligned, damage can occur very quickly to the groove or cam face. Also, such misalignment can cause failure of the pin with the above described results. Therefore, extreme care is used in constructing these tools, which makes fabrication costs quite expensive.
Accordingly, it is a primary object of this invention to provide an improved tool for fishing an object from a bore hole that aids in preventing damage to a pin used in the camming mechanism.
A further object of the present invention is to provide an improved tool for fishing an object from a bore hole that aids in preventing damage to the fingers used to grip the object.
A further object of the present invention is to provide an improved tool for fishing an object from a bore hole that permits the use of a stronger spring than used in the prior art fishing tools.
An additional object of the present invention is to provide an improved tool for fishing an object from a bore hole that employs a single pin in the camming mechanism.
In accordance with the invention, a tool for fishing an object out of a bore hole is disclosed. The tool has a tubular body with an upper end for connecting an apparatus extending from the earth's surface to raise and lower the tool in and out of the hole and a lower end for extending around and over a portion of the object, the lower end having a tapered surface located thereon. Fingers are mounted within the body for coacting with the tapered surface of the body to move between an opened position and a closed position with a spring being mounted within the body for urging the fingers toward the lower end of the body to coact with the tapered surface. A camming means is mounted within the body for controlling the movement of the fingers between the opened and closed positions by using a sleeve rotatably mounted within the body, which forms a cam face defining "J" slotted grooves with upwardly extending stems at the opened and closed positions of the fingers and connecting grooves between the "J" slotted grooves to form a single cam groove which permits recycling of the fingers between the opened and closed positions. The pin of the camming means extends from the body into and coacts with the cam groove to cause the sleeve to rotate between the opened and closed positions by moving the body toward and away from the object after engagement with a portion of the object, the fingers moving into the closed position by the urging of the spring and by the movement of the pin upward into the closed position stem of the "J" slotted grooves and the fingers moving into the opened position by overcoming the urging of the spring and by the movement of the pin upward into the opened position stem of the "J" slotted grooves. Lugs are mounted with the sleeve for nesting within corresponding slots formed in the body which define first shoulders between the slots and second shoulders at the bottom of the slots, the lugs have downwardly facing shoulders for abutting against the first shoulders to limit movement of the pin in the opened position stem of the "J" slotted grooves and for abutting against the second shoulders to limit movement of the pin in the closed position stem. The opening and closing of the fingers and movement of the lugs is caused by moving the body toward and away from the object which causes the first and second shoulders to move downwardly relative to the lugs and the pin to move downwardly within and coact with the cam groove for rotating the sleeve and lugs into alignment such that the downwardly facing shoulders of the lugs will abuttingly engage the respective first or second shoulders of the body.